In the photographic arts, as low cost computer processing became available, technology emerged for generating an electronic scan of film in order to capture and store digitized electronic images from the film. These scans were useful for archival and editing purposes, image enhancement and processing, and the like.
Emphasis in the development of such scanners was upon those adapted for transparencies and, more particularly, for mounted transparencies as opposed to negative films for several reasons. The term "film" will be used hereinafter generically to include such transparencies except where in context it is apparent that a strip of film is intended.
This emphasis on transparencies was notwithstanding that in many respects negatives are superior to transparency technology. For example, cost of film and processing for negatives may perhaps be half of that for transparencies. Negatives also require less time to process and fewer chemical steps, and typically provide better quality over wide exposure ranges, having a gamma or signal level less than half that of transparencies, allowing a much greater brightness recording range. While this in turn normally makes dust, scratches, and other anomalies more noticeable, with the advent of computer image processing this drawback may now be overcome. See, for example, U.S. Pat. No. 5,266,805, issued Nov. 30, 1994 and entitled System and Method for Image Recovery.
A consequence which results from such quality is that negatives may also be archived in less space. Because of the increased dynamic range, quality, contrast and the like, there are fewer rejects and therefor fewer photographs needed to be taken for a given situation if archived as negatives rather than as transparencies. The effects of selecting multiple filters and apertures or exposures could be simulated by computer processing of negatives to emulate the wide variations associated with these techniques more conventionally obtained with transparencies. The equivalent to multiple transparency exposures could thereby be simulated with post computer processing of negatives to compensate for or simulate daylight, fluorescent or incandescent lighting, color effects, etc. whereby the post-processor could be employed to select and vary the colors and resolutions. In other words, the "bracketing" technique commonplace in the photographic arts with transparency work could be eliminated with scanned negatives.
With all the foregoing obvious benefits to working with negatives, an explanation is helpful as to why, until recently, scanner development nevertheless still focused upon transparency work and particularly mounted transparencies. First, most published pictures are generated from transparencies for numerous reasons. For example, lithographers typically feel that better results are obtained from transparencies than from prints obtained from negatives (which by definition are second generation images). Although negatives have a much wider brightness recording range than transparencies, transparencies have a wider range than prints made from the negatives. The inconvenience of and necessity for prints for an art director to review when working with negatives and the lesser quality of such prints compared to transparencies thus gave rise to the popularity of transparencies over negatives.
With prints heretofore as the main practical presentation medium for negatives, the numerous favorable aspects of negatives hereinbefore noted were thus not generally being realized. The necessity of prints from negatives was resulting in the most costly imaging systems, with the lowest quality, and the most difficulty in archiving.
With the advent of computer scanning and imagery, the emphasis has continued to be on scanning of transparencies and more particularly mounted transparencies, notwithstanding the benefits of negatives. The scanning of "slides" has become a common practice for computer image capture and processing. Secondary to the scanning of slides has been the scanning of film transparencies, which has received much less development work for several reasons. In such scanners a scanning element effects a linear motion across the film surface in a direction transverse to the longitudinal axis of the filmstrip. Such linear motion was frequently found to present numerous problems. For example it was difficult to provide for the linear scanning motion in an inexpensive manner which nevertheless provided for high resolution in the scanning process.
It was also commonplace for strips of film to exhibit curvature which, upon scanning, results in serious focus distortions. In an effort to solve this problem, one approach was to provide the linear scanners with a transparent cover over the transparency film, thereby presenting a flat surface to the scanner. While this solved the aforementioned distortion problem, yet other problems were thereby introduced, namely the scratching and other degradation of the film surface by the cover in contact with the film, and additional dust and foreign material on the cover itself.
In another type film holder, the image being scanned was not covered, but was held by pressing adjacent film against a flat surface, thus only adjacent images were exposed to scratching and transfer of dust, and the image being scanned was not as precisely held flat.
Yet another drawback of such scanners was that they were typically limited to relatively short, non-continuous strips. This was due to the aforementioned need to maintain a flat film surface to present to the scanner.
Still another problem associated with typical such transparency scanners was that again, in order to maintain a flat scanning surface, the sides of the filmstrip were typically held by various mechanical contrivances. This thereby limited the flexibility with which one was able to vary the horizontal width of the scan to the maximum extent necessary to capture an image (which may extend close to the edge of the strip).
For all the foregoing reasons, it was highly desirable to develop a film scanner adapted for scanning negative filmstrips which (with the advent of inexpensive computer processing) could capitalize on the vast potential provided by capturing negative images from filmstrips for subsequent postprocessing.
It was a further object of the invention to provide a transparency film scanner which would present a substantially flat film surface to the scanner, thereby avoiding edge focus problems.
Yet another object of the invention was to provide such a surface in a manner which would avoid damage to the film surface rising from contact therewith, such as surface scratches and the like.
It was still a further object of the invention to provide for such a scanner which could accommodate longer filmstrips while obviating the need for linear film magazines or the like which would otherwise become impractical with long filmstrip segments.
It was yet an additional object of the invention to provide for such a scanner which might operate in a continuous fashion over the entirety of the extended filmstrip.
A further object of the invention was to provide for such a filmstrip scanner which could improve the accuracy of the scanning by means of rotary motion.
These and other objects and benefits of the invention are achieved and may be better understood with reference to the accompanying figures wherein: